Mercury type circuit breaker



W. l. MCLAUGHLIN MERCURY TYPE CIRCUIT BREAKER Filed Nov. 22, 1952 FZ. o im ,3M mxj' 952 3| f7 W n? 5 4o Oct. 11, 1955 1N V EN TOR.

United States Patent O 2,720,562 NIERCURY TYPE CIRCUIT BREAKER- William I. McLaughlin, Los Gatos, Calin Application November 22, 1952, Serial No'. 321,998 4 Claims. (Cl. 20o-3 2) This invention relates' broadly to electrical switches and more particularly to a mercury type switch and novel means for compensating for expansion and contraction of the mercury therein. v

In the past, a great deal of research has been conducted with a view of eliminating hard metal contact points in switch structures to thereby avoid the expense and trouble caused by arcing and pitting of these contact points. With the exception of vacuum tube mercury type' switches little progress has been made in alleviating the deficiencies-and problems entailed with hard metal contact points. I have discovered by experiment that a short rubber tube filled with mercury and plugged at both ends with lead wires serves as a circuit breaker when the tube is pinched to separate the mercury within the tube. While this division of a column of mercury into two insulated halves satisfactorily eliminates most of the deficiencies of metal contact points, it too has its faults due to time lag Vbetween open and closed positions, i. e., the return of the mercury to' a single column after the pinching of the rubber tube is released.

The present invention is directed to a novel matter of maintaining the mercury within a ilexible tube under constant pressure but yieldable to compensate for displacement within such tube when the latter is pinched.

Another object is to provide a deformable mercury containing tube with a confining shell for resisting ination of the tube when the latter is pinched and the mercury therein compressed.

Yet another object is to provide a housing vfor a deformable mercury containing tube with a' relief chamber communicating with one end of such tube to compensate for displacement of the mercury within the tube when the v y x by' aplug 31 of electrical conductive material having conlatter is pinched. In connection withv the foregoing, it `is another object to provide a tube pinching plungerdisposed to pinch the mercury tube at a' point remote from the relief means to' transmit most or alll of the' compressive for'ce against the mercury toward the relief means:

Another object is to provide a relief or compensating means in combination with a deformable type mercury switch with means for maintaining the mercury within the switch under a substantially constant pressure to thereby assure prompt circuit closing action upon release of the pinching action against the deformable tube.

These and other objects' and `advantages of the present invention will become more apparent from a reading of the following description and claimsv in the light of the drawings in which:

Fig. l is a longitudinal section through a' mercury switch embodying the present invention.

Fig. 2 is a view similar to that of Fig'. l but showing parts thereof in a different position.

Fig. 3 is a longitudinal section' through a similar form of mercuryv switch entirely encased within a housing.

Fig. 4 is a cross section of Fig. 3V taken substantially along line 4-4 in Fig. 3; and

Fig. 5 is a diagrammatic illustration of one of the many uses to which the present switch may be put. i

In the drawings, I have shown a switch assembly 1:0 including a deformable tube f1 which may be oflrtbber, plastic or the like having its ends closed .by electrical conductor members for confining a quantity of'mercury 12 between the closed ends ofthe tube" 121 for pinching Patented- Oct.'v 11,. 1955 rice 2 the tube to separate the mercury therein into two separated columns insulated from each other to break the electrical circuit between the electrical' conductor members at the ends of the tube.

In accordance with the presentinvention, the foregoing simple mercury switch structure is confined within a metal housing 13 having an internal chamber 14 formed therein of a size to receive the deformable tube 11 for maintaining the latter' in its normal state of expansion but permitting the latter to be pinched in the manner as shown in Fig. l bythe means 1'2'. In thisl connection, the housing'1-3 further includes a guide sleeve I6 having its axis disposed perpendicular to the axis ofV the chamber 14 and tube I1 for guiding a plunger 17 for movement toward and from the deformable tube'. The plunger 17 is urged: by a spring 18 into ineffective position away from the tube 11, and has its free end 19' disposed in engagement with an actuatingI mechanism- 20, for example, a `cam 21 on a rotor shaft 22'.

For purposes of illustration, I have shownthe switch housing.- 13' in Fig.k l mounted on an `arm 23 having one end'pivoted on a stud yshaft 2'4 which is stationary and itsl other end adjustable relativeL to ya stud boltl 25 for movement towardv and from the rotor shaft 22. The rotor shaft 22 revolves about an axis parallel to, the stud shaft 24 and is fixed relative thereto so that the free endv 1'94 of the plunger always engages the periphery of thecam 21. As illustrated, the cam 21 has its periphery provided with an acclivit'y 26 which extends a greater radial distance from the balance of the periphery' which forms the declevity' surface 27 of the cam. Consequently, when the free end 19(v of the plunger rests on the declevity 27 the inner end 3'0" of the plunger is disposed just out of the chamber 14 as shownI in Fig'. 2'. Contrariwise, when the acclivvity 26 is radially' in alignment with the axis of the plunger the inner end 30 of the latter is disposed within the chamber 14 pinching the tube 1'1 as shown in- Fig. l. Obviously, very many different arrangements of actuating mechanisms may b'e employed, the present disclosure being' for p'urliosesl of illustration only'.

As seen in Figs. land 2, one end of the tube 11 is sealed nection' with a wire'32 on one side of an electric circuit 33, diagrammatically illustrated. The other end of the tu'be 11` ha's open communication with a chamber C provided atlone end of a cylinder 34. The cylinderv 34 has a round' nipple' neck 43 upon which the open end of the tube 11' is stretched. Cement is applied to the nipple neck 43 so `as to obtain a :good seal between the latter and the tube .11.. The cylinder' 34 has a bafe or diaphragm 35 arranged therein for cushioning the pressure of the mercury as it is compressed ywithin the `tube 11. In the present disclosure, the baffle is in the form of a piston arranged in the cylinder 34 for reciprocation which piston 35 has asuitableY sealngring. 36v arranged in an annular ring groove 37 for maintaining sealed contact with but affording' slidingmoveme'nt of the' piston relative to said cylinder. The opposite end of the cylinder is' suitably closed by a cap against which a compression spring39 bears, the opposite" end of which spring bears against the piston 35 to maintain the latter in its eXtreme position away from the ap 3s. I

Fr'fon'fl the foregoing it will be seen that the mercury M confined within the tube 11 contacts the piston to complete the electrical circuit via the spring 39 and cap 38 to an electric wire 4`0`.0n Vthe ground side of the electric circuit 33. Consequently, when'the column of mercury is divided by pinching'vof the tube 1I as seen in Fig. 1- the circuit 33 isjb'roken. More important, however, is the fact thatv upon pinching of the tube 11 to break the circuit, the mercury isy displaced within-t'hetub'e` and into the chamber C provided the' cylinder 34. The pressure of the displaced mercury against the piston 35 causes the latter to be displaced within the cylinder against the action of the compression spring 39. The spring 39 is calculated to yield due to displacement of the mercury and piston but also to maintain a uniform pressure against the piston and mercury to assure prompt return of the mercury to a full column upon release of the plunger from pinching relation against the tube 11. Note also that there is a reserve space provided within the chamber C to aid in keeping the entire area of the mercury side of the piston 35 in constant contact with the mercury M. This assures uniform back pressure of the mercury against the piston and a true balance with the counterpressure afforded by the spring 39.

In addition to the foregoing, it will be noted, especially in Fig. 3, that the plunger 17 is disposed more closely to that end of the mercury column or tube which is remote from the pressure compensating chamber, piston and cylinder. In this manner, very little of the mercury is coniined in the far or dead end of the tube 11 when it is pinched by the plunger. In other words, the greater quantity of the mercury is in communication with the live end of the tube 11 which opens to the pressure compensating chamber C so as to relieve the tube itself from excessive strain. It should be understood, however, that since the tube 11 is wholly confined within the housing 13 any tendency of the tube to bulge or expand beyond its normal diameter or size is minimized if not completely eliminated.

Refer now to Fig. 3 wherein I have shown a more simplied construction of mercury switch embodying the principle of the present invention. In this form of construction, the housing 13 consists of a solid block which, if desired, may be a split block adapted to be secured together by suitable bolts b in the conventional manner. This housing 13' has an elongated main passage 14 one end 15- of which is of reduced size and a shorter passage 16 disposed perpendicular to the main passage andk very near that end thereof which is of reduced size.

The deformable tube 11 is encased in a shell S having an ovoid internal passage O, as best seen in Fig. 4. This ovoid passage receives the otherwise round tube 11 to maintain the latter in an oval shape within the shell S. The shell S is inserted at the larger end of the main passage 14', the inner end of the shell engaging the shoulder 40 adjacent the reduced end 15' of the passage. Part of the tube 11 extends into this reduced end 15 of the passage 14' and receives the conductor plug 31 connected to the wire 32. as before. A non-conductive or phenolic washer 41 is placed against the extreme end of the tube 11' and is locked in place by a snap ring 42 seated in an annular groove provided in the reduced passage 15.

The opposite end of the tube 11' fits over a round nipple neck 43 formed on one end of a cylinder 34'. The nipple 43 is suitably cemented to the tubing which is stretched around the nipple. The same cementing is applied to the conductor plug 31 around which the opposite end of the tube is stretched. In each case a spring ring clamp 44 surrounds the tube to secure the latter against the conductor plug and the nipple, as the case may be, to assure a pressure seal at the ends of the tube.

The cylinder 34 is much the same as the one illustrated in Figs. l and 2 in that it provides a chamber C communicating with mercury M' in the deformable tube. It also has a piston 35 therein as well as a compression spring 39 but is not capped in the same manner. In this form, the open end of the cylinder 34 is closed by a conductive washer 45 connected to a wire 40. A phenolic washer 46 lies flush against the conductive washer 45 and is held in place by a snap ring 47 suitably seated in an internalannular groove 48 formed adjacent the open end of the main passage 14 in the housing 13'.

Referring now to the shorter passage 16 which is perpendicularly disposed to the main passage 14', a plunger 17 is arranged for reciprocation in this shorter passage 16. The plunger 17' has a tube engaging head 50 which isV substantially the same 'width as the ovoid passage O.

This widened head 50 is disposed in a slot 51 cut into the shell S for guiding the plunger 17 for reciprocation into and out of the main passage 14. The plunger 17 has a ange 52 formed thereon against which one end of a compression spring 18 bears. The opposite end of the spring 18' bears against a guide sleeve 53 which lits snugly in the passage 16' and is held in place therein against the action of spring 18 by a snap ring 54. The snap ring iits into an annular groove 55 formed in the internal wall of the passage 16 so as to secure the guide sleeve 53 in place for maintaining constant spring pressure against the plunger 17. In this manner the head 50 of the plunger is constantly urged into tube pinching position as seen in Fig. 3.

The free end 56 of plunger 17' is shown connected to the armature of a solenoid 57 which is normally deenergized but is adapted to be energized upon completion of an electrical circuit 33"diagrammatically illustrated. In this manner, the solenoid coil, when energized, will overcome the action of spring 18 to attract the plunger 17 away from the tube 11 to allow the mercury M' to complete circuit between the wires 3240. It should here be noted that the plunger arrangement in Fig. 3 can be made to operate in the fashion illustrated in Figs. l and 2 by changing the disposition of the ange 52 relative to the plunger 17 so that this liange bears against the guide sleeve 53. Thus the compression spring 18 can be disposed between the ange 52 and the shell S to normally maintain the head end 50 of the plunger out of the main passage 14 and within the slot 51. Consequently, the free end 56 of the plunger 17 can be disposed against a cam for operation in the manner as hereinbefore explained in connection with Figs. l and 2.

Either of the above explained forms of switches can be used in many different arrangements for making and breaking an electrical circuit. One such arrangement is illustrated in Fig. 5 wherein a plurality of switches 10 have their plunger disposed in actuating contact with a like number of cams. In this arrangement each switch is closed in sequence to illuminate lamps L successively to spell out letters on a sign and/or to illuminate all lamps L simultaneously so that the entire wording on a sign can be read.

Switches suchvas those illustrated in the accompanying drawings have been used with success as a commutator for an internal combustion engine. Due to the complete elimination of arcing these switches are exceptionally useful in hazardous locations such as near explosives, gasoline, or where dust particles or vapors form an explosive mixture with air.

At all events, the provision of means for maintaining thet mercury under constant pressure, i. e., neither too high nor too low, assures positive and prompt action of return of the mercury to a single column or circuit closing condition. Moreover, since the mercury tube of the present invention is completely encased within a housing it can never expand beyond its normal shape. This saves the deformable tube from stretching or bulging and keeps the mercury under most favorable conditions. Should the mercury within this switch expand or contact due to temperature changes, such expansion and/or contraction is compensated for by the spring loaded piston within the chamber or reservoir C.

While I have described the foregoing switch structure in specific detail it will be apparent that it is susceptible to variations, modifications and alterations without departing from the spirit of my invention. I, therefore, desire to avail myself of all variations, modifications and alterations as fairly come within the purview of the following claims.

vWhat I claim as new and desire to protect by Letters Patent is:

l. In an electric switch of the type having a deformable tube containing a column of mercury adapted to be separated by pinching of said tube; a housing for conining said tube to its normal shape, a chamber formed within said housing in axial alignment with said tube and communicating with one end of said tube for receiving mercury therefrom when said tube is pinched, a cylinder in said chamber having an open nipple neck secured to said one end of said deformable tube, a piston in said cylinder, a cap for closing that end of said cylinder opposite the nipple neck thereof and yieldable means between said cap and piston for maintaining said piston in constant contact with the column of mercury confined within said tube.

2. In an electric switch of the type including a deformable tube having means sealing one end thereof connected to an electrical conductor, a second electrical conductor means connected to the opposite end of said tube, a body of mercury lling the interior of said tube, and means reciprocable toward and from said tube for separating the mercury therein into two isolated masses, the combination with said second electrical conductor means of a cylinder providing a chamber communicating with said opposite end of said tube for receiving mercury therefrom, a baiile in said chamber adapted to yield upon an increase of pressure in that mass of mercury communicating with said chamber, an electrical conductive cap on said cylinder and electrical conductive means between said cap and baille cooperating with said baffle for maintaining a constant counterpressure against the latter and the mass of mercury in said chamber for promptly forcing the latter toward said tube when said reciprocable means moves away from said tube.

3. In an electric switch of the type including a deformable tube containing a column of mercury adapted to be separated upon pinching of said tube; a combined electrical conductor and pressure compensator comprising a housing having a passage confining said deformable tube to its normal shape, a lead wire secured in one end of said tube, a cylinder axially aligned with said tube and having a reduced nippled end secured to the other end of said tube, a cap for closing the opposite end of said cylinder, a lead wire connected to said cap, a baille within said cylinder, and means for electrically connecting said batlie to said cap and for yieldably urging said baie against said column of mercury for maintaining the latter under uniform pressure.

4. In an electrical switch of the type including a deformable tube containing a column of mercury adapted to be separated upon pinching of said tube; a combined electrical conductor and pressure compensator comprising a cylinder having a reduced nipple at one of its ends secured to one end of said tube in axial alignment with the column of mercury in said tube for admitting mercury into said cylinder upon pinching of said tube, a piston in said cylinder, a cap on the other end of said cylinder, a lead Wire connected to said cap, and a spring between said piston and cap completing the circuit from said column of mercury to said lead wire and for maintaining said cylinder in constant contact with said column of mercury and the latter under constant pressure.

Sigman Dec. 4, 1934 Becker Mar. 26, 1940 

